Spark-plug for internal-combustion engines.



M. G. KOPF.

SPARK PLUG FOR INTERNAL COMBUSTION ENGINES.

APPLICATION FILED 1uLY21. 1915.

1,216,139. Patented Feb.13,1917

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UNITED STATES PATENT oEEroE.

MELROSE Gr. KOPF, OF DAYTON, OHIO, ASSIGNOR TO MCCORMICK MANUFACTURING COMPANY, OF DAYTON, OHIO.

Specification of Letters Patent.

Patented Feb. 13, 1917.

Application filed July 21, 1915. Serial N0. 41,065.

To all whom it may concern: Be it known that I, LIELROSE G. Korr, a, citizen of the United States, residing at Dayton, in the county of Montgomery and State of Ohio, have invented certain new and useful Improvements in Spark-Plugs for Internal-Gombustion Engines, of Which the following is a specification, reference being had therein to the accompanying drawlng.

This invention relates to spark plugs for internal combustion engines. As is well known, in the practical operation of engines of this type, there is formed within the cylinder of the engine a quantity of carbon which is deposited on the various parts with in, or in open communication with, the cylinder, and ambng these parts is the spark plug. This deposit of carbon establishes an electrical connection between the electrode carried by the porcelain core of the plug and the shell or supporting casing for the core. A heavy deposit of carbon will, of course, result in practically short circuiting the plug while minor deposits will result in .a leakage between the electrodes which will be more or less serious and will afiect the efficiency of the plug in proportion to its extent. It is seldom, if ever, that the conditions under which an internal combustion engine operates are such that no carbon is formed within the c linder. Under superior conditions the deposit will be very light and may, in fact, be practically invisible to the eye, but its presence will result in leakage of current from the electrode along the surface of the core to the shell.

The object of the present invention is to provide a spark plug, the core of which will be so constructed as to efi'ectually eliminate this leakage. To this end it is a further object of the invention to provide a core or spark plug having portions of the surface between the electrode and the shell of such a character that the carbon will not accumulate thereon. It is also an object of the portion 2 hollow and provided with exterior screw threads, by means of which the plug is mounted in the cylinder of the engine.

The upper portion of the shell, 3, constitutes a nut and is provided with internal screw threads to receive the bushing 4c. Mounted in the shell is a body or core 5 of insulating material, such as porcelain. This core has an enlarged portion 6 fitting within the upper part 3 of the shell and forming a shoulder to engage the bushing 4;, by means of which the core is secured within the shell. The lower portion 7 of the core extends into the hollow lower portion 2 of the shell and is spaced away from the walls thereof. The core has mounted therein an electrode 8 which preferably extends lengthwise oi the same and is provided at its outer end with a binding post 9. A second electrode 10 is carried by the shell 1. The arrangement of the electrodes may vary, but, as here shown, they have their end portions arranged substantially parallel, as this arrangement gives a spark of longer duration. The construc tion so far described is a standard spark plug construction and forms no part of the invention. To prevent the accumulation of carbon upon that part, 7, of the core, which extends into the hollow portion 2 of the shell, which is in open communication with the interior of the engine cylinder, 1 provide said portion of the core with one or more annular projections or ribs 11 which extend about the electrode 8 and separate the same from the shell. The number and arrangement of these ribs may be varied according to the circumstances, but where the core has an elongated body portion such as that here shown, I prefer that the ribs should be arranged circumferentially, and that there should be several of them. These ribs have rather thin edges which are 8X- posed to the heat of the explosions within the cylinder, and which will be heated by such explosions to a degree sufficiently high to consume the carbon which is deposited upon these edges, thereby keeping the edges of the ribs free from such deposits and interrupting the continuity of the conducting v to a person skilled in the art.

surface formed by the carbon deposit. in

the case of a-porcelain core, the edges of the.

ribs may, at the time of explosion, be rendered incandescent, but this condition will be temporary only, and, because of the contiguous body of the core, the heat in the edges of the ribs will be so dissipated prior to the compression of the next charge, that there will be no danger of the charge being prematurely ignited. To secure the best results ll prefer not only to' space the several ribs apart but to so arrange them that the edge of each successive rib will project slightly beyondthe line of the preceding rib, thus exposing the edge of each rib directly to the flame and the heated gases resulting from the explosion. This is best accomplished by giving theportion '4' of the core a tapered shape, as in this manner it is unnecessary to form the upper ribs of excessive length. l have also arranged the several ribs on lines extending obliquely to the axis or length of the core, thus .giving them what may be termedan umbrella shape. in this manner a relatively thin edge can be provided on the projection without materially weakening the construction. By providing one or more such projections between the electrode and the point of contact betweenthe core and the shell, there is provided not only an elongated surface over which the current must travel, but this sur-' understood that l do not desire to be limited to the details of construction shown and described, for various modifications will occur Having thus fully described my invention, what i claim as new and desire to secure by Letters Patent, is:

L core of insulating material for a spark lug comprising a body portion tapered toward that end thereof at which the spark isformed, and provided on the tapered portion thereof with the plurality of circumferential projections of substannaraiae v tially equal width, each projection having its vcircumferential edge of such thickness that it will be so heated by the explosions produced by the sparks from said spark plugas to cause any conductive matter which may 7 of each successive projection extending beyond the edge of thepreceding projection, said edges being of such thickness that they will be so heated by the explosions produced by the sparks from said 'plug as to cause any conductive matter which may have beendeposited thereon to be consumed.

3., A core of insulating material for a" spark plug, comprising a body portion having at one end an electrode and provided with a plurality of circumferential projections, spaced apart and each decreasing in thickness from said body portion toward the edge of the projection, that projection nearest said electrode having the shortest diameter, and each successive projection having a diameter greater than the diameter of the preceding projection.

4t: lin a spark plug, a supporting casing having its inner end open, a core of insulating material mounted within said casing, and an electrode carried by said core near the open end of said casing, said core having a series of circumferential projections arranged within said casing, spaced apart and interposed between said electrode and said casing and each provided with an edge adapted to be so heated by the ex plosions produced by the sparks from said plug as to cause any conductive matter de- 

